Deoxidizing multilayered body and method or manufacturing the same

ABSTRACT

An oxygen absorbent is provided which includes a multilayered body formed from a plurality of thin resin layers laminated over one another. At least one laminated side of this multilayered body is constructed as an oxygen-absorbing surface. The multilayered body includes an oxygen-absorbing layer of a resin composition in which an oxygen-absorbing component is dispersed and which is made porous; a non-porous oxygen-permeable layer which is permeable to oxygen; and a porous oxygen-permeable layer which serves as a protection layer for the non-porous oxygen-permeable layer. The layers are thermally bonded to one another and the resulting laminate is drawn to simultaneously enlarge the pores in the porous layers.

TECHNICAL FIELD

The present invention relates to an oxygen-absorbing multilayered bodyfor absorbing oxygen and a manufacturing method thereof. Moreparticularly, this oxygen-absorbing multilayered body is formed in afilm or sheet shape which is preferable as a packaging material. Theoxygen-absorbing multilayered body generally has a multilayeredconstruction and is provided with water and oil resistance. Thisfilm-shaped or sheet-shaped oxygen-absorbing multilayered body is usedas a container or package to preserve various kinds of products such asfood, medicines and metal products which tend to easily deteriorate dueto an influence of oxygen in order to prevent such products fromoxidizing.

BACKGROUND ART

In order to prevent various kinds of products such as food, medicinesand metal products, which tend to easily deteriorate due to an influenceof oxygen, from oxidizing, oxygen absorbers which remove oxygen from apackaging container or packaging bag have been used. The form of theoxygen absorber which was developed at an earlier stage and is stillgenerally used is a sachet which is filled with a granular or powderyoxygen-absorbing component.

As an oxygen absorbent which can be handled easily, can be widelyapplied and will not cause problems such as eating it by mistakes, afilm- or sheet-shaped (hereinafter sometimes simply referred to as"film") oxygen absorbent exists. This film-shaped oxygen absorbent isused on a packaging container or packaging bag itself. In this case, itis possible to give oxygen-absorbing performance to the packagingcontainer or packaging bag itself.

In order to obtain a film-shaped oxygen absorbent, a technique exists toprepare a resin composition by using a thermoplastic resin as a matrixcomponent and by fixing a granular or powdery oxygen-absorbing componentin the matrix component, and to make the resin composition in amultilayered form with other resin layers.

However, the use of this oxygen-absorbing multilayered body sometimescauses the oxygen-absorbing component to contaminate the content of acontainer when the oxygen-absorbing layer directly contacts a packagedsubstance such as food, particularly when the content is liquid.

Therefore, as shown in the Japanese Patent (Kokoku) Publication No. SHO62-1824 and the Japanese Patent (Kokoku) Publication No. SHO 63-2648, amultilayered construction has been devised, in which both sides of theoxygen-absorbing layer are covered with resin layers. For example, theabsorbing surface, which is located on the packaged substance side ofthe oxygen-absorbing layer, is shielded with an air-permeable materialand a gas-permeation-resistant layer is placed on the other side of theoxygen-absorbing layer.

If a porous air-permeable material is used for the shielding layer onthe absorbing surface of the oxygen-absorbing layer, theoxygen-absorbing component leaks out toward the packaged substance whichcontains a large amount of moisture. Therefore, it is desirable that theshielding layer is made of a resin layer having no fear of such leakage.

A known oxygen absorber is used as the oxygen-absorbing component to bemixed in the oxygen-absorbing layer. Particularly, iron powder which issuperior in the oxygen-absorbing performance is often utilized as a mainelement for the oxygen-absorbing reaction.

However, the oxygen absorption speed of the conventional oxygenabsorbent has remained extremely low. This is because the oxygenpermeability of a polyolefine-group resin used as a resin in which theoxygen-absorbing component is mixed is comparatively low, and becausethe oxygen permeability of the resin shielding layer which covers theabsorbing surface of the oxygen-absorbing layer is also low. In otherwords, the oxygen-absorbing component of the oxygen-absorbing layer isblocked by the resin of the matrix component of the oxygen-absorbinglayer and the resin of the shielding layer.

In order to improve the oxygen absorption speed of the oxygen-absorbinglayer, as shown in the Japanese Patent Laid-Open (Kokai) Publication No.HEI 2-72851, it is known to form the oxygen-absorbing layer by drawing aresin composition sheet, which is made by mixing and kneading theoxygen-absorbing component containing iron powder as its main element ina thermoplastic resin, so that the resin composition sheet is mademicroporous. Moreover, the Japanese Patent Laid-Open (Kokai) PublicationNo. HEI 2-72851 and the Japanese Patent Laid-Open (Kokai) PublicationNo. HEI 5-162251 describe the technique to draw a multilayered body, inwhich a shielding layer of a resin composition made by mixing abarely-water-soluble filler in a thermoplastic resin is laminated over aresin composition layer containing an oxygen-absorbing component, sothat the resin layer containing the oxygen-absorbing component and theshielding layer are made microporous.

In this case, drawing breaks the interface between the filler and theresin, thereby making micropores. More micropores are connected to eachother, causing the entire body to become a continuously porous body.Accordingly, shielding of oxygen permeation by the resin portiondecreases and, therefore, the oxygen absorption speed (air permeability)considerably improves. Although it is a porous body, if non-polar orlow-polar macromolecules are used, water in a liquid state will notpermeate due to the water repellency of such macromolecules.

As described above, The oxygen-absorbing film in the form where thecontinuously porous oxygen-absorbing layer is covered with thecontinuously porous shielding layer realizes a high oxygen absorptionspeed and may be considered as a superior oxygen absorbent which has noproblem of contamination when it is used for a short period of time evenif the content contains much water.

However, when any liquid having relatively low polarity (for example,when water is not used solely, but is used with an addition of variouskinds of fats, oils and alcohol) exists in the content such as food,there is a problem in that the liquid permeates into the micropores ofthe continuously porous portion and, through the path of such a liquidphase, the oxygen-absorbing component leaks out of the oxygen-absorbingfilm, causing the contamination of the content.

Also in the case of water, if a gas in the micropores dissipates (forexample, dissolves into a liquid) when the oxygen-absorbing body is leftfor a long period of time, the oxygen-absorbing component sometimessimilarly leaks out. It is possible to, for example, use afluorine-contained agent for treatment in order to give, for example,oil repellency. However, since it will bring about a new fear ofcontamination by the agent, it is desirable not to use it if possible.

From the viewpoint of preventing the problem of leakage of theoxygen-absorbing component toward the packaged substance, it isdesirable that the shielding layer of the oxygen-absorbing layer be aresin layer which is made non-porous. However, if the resin layerbecomes thick, the oxygen permeability will not be sufficient. Then,there are known examples in which a thin resin layer is used as theshielding layer. For example, the Japanese Patent Laid-Open (Kokai)Publication No. HEI 5-318675 suggests an oxygen-absorbing multilayeredsheet concerning which the oxygen-absorbing resin layer which has beendrawn and made microporous is coated with resin.

DISCLOSURE OF THE INVENTION

The oxygen-absorbing sheet concerning which a thin non-porous coating ofthe shielding layer is directly formed over the oxygen-absorbing layerhas a problem of strength in that the oxygen-absorbing component of theoxygen-absorbing resin, particularly iron powder or particles, protrudesover the sheet surface or the shielding layer at the step ofmanufacturing the oxygen-absorbing sheet or during the handling of theoxygen-absorbing sheet. Moreover, there are fears that theoxygen-absorbing component may move from the shielding layer to thepackaged substance. If a thickness of the shielding layer is then madethicker, the air permeability will be diminished, thereby resulting inlowering of the oxygen absorption performance.

It is not practically easy to form a film-shaped oxygen absorbent whichis provided with substantially sufficient oxygen permeability bylaminating a thin non-porous resin film over the oxygen-absorbing resinlayer. Particularly, it is not easy to produce a thin film-shapedoxygen-absorbing multilayered body for a business purpose. Since theoxygen-absorbing resin layer contains a foreign substance such as ironpowder, if known laminating methods such as an extrusion laminatingmethod and a coextrusion laminating method are applied, there will befilm processing problems in that iron powder may break the thin film andcreate pinholes or unevenness may be formed on the surface. Even if athin non-porous coating is pasted over the oxygen-absorbing resin layer,if a pasting method is applied, it is difficult to manufacture theoxygen-absorbing multilayered body by laminating the shielding layer ofa thin non-porous film.

The fact is that concerning the prior art, there is no film-shaped orsheet-shaped oxygen-absorbing multilayered body which has no fear ofleakage of the oxygen-absorbing component and is superior in the oxygenabsorption performance when it is used as a packaging material for aliquid substance.

An object of the present invention is to provide an oxygen absorbent ina multilayered construction and particularly in a film shape or a sheetshape, which is superior in the oxygen absorption performance and ofwhich oxygen-absorbing component will not move or leak out toward thepackaged substance. Another object of this invention is to provide anoxygen absorbent of which resin component will not leak out toward thepackaged substance. A further object of this invention is to provide anoxygen absorbent of which oxygen-absorbing component will not protrudeover the surface of the oxygen-absorbing multilayered body. A stillfurther object of this invention is to provide a method formanufacturing such an oxygen absorbent.

Among the layers of the oxygen-absorbing multilayered body of thisinvention, a non-porous layer as a first oxygen-permeable layer, aporous layer as a second oxygen-permeable layer, and a porousoxygen-absorbing layer are formed by multilayer simultaneous drawing.Concerning a gas-permeation-resistant layer, it is possible to add sucha layer either by including the gas-permeation-resistant layer in theabove-described plural layers and applying the multilayer simultaneousdrawing to these layers or by laminating the gas-permeation-resistantlayer after the multilayer simultaneous drawing of the above-describedlayers. If the multilayer simultaneous drawing is conducted by includingthe gas-permeation-resistant layer, a resin which can be drawn and whichhas a low oxygen permeability may be simply laminated prior to thedrawing. If the gas-permeation-resistant layer is laminated after thedrawing, various methods can be utilized such as bonding or fusion ofvarious kinds of gas-permeation-resistant films, extrusion coating of aresin having a low oxygen permeability, or vapor deposition of variouskinds of substances having a low oxygen permeability.

Considering that not only the resin material which can be drawn, butalso other various kinds of materials which are superior in oxygenshielding ability are used, and that an individual name (such as foodname) of an object of oxygen absorption is to be printed on thegas-permeation-resistant layer side, the method of laminating thegas-permeation-resistant layer after the drawing of a plurality oflayers other than the gas-permeation-resistant layer is more applicablein the manufacture and use. Since the resin which can be drawn and whichhas a low oxygen permeability generally contains hetero atoms, a meltingtemperature becomes relatively high and, therefore, it is oftendifficult to simultaneously draw the resin with other layers.Accordingly, it is desirable to laminate the gas-permeation-resistantlayer afterward.

However, if a plurality of layers other than thegas-permeation-resistant layer are drawn and thegas-permeation-resistant layer is then laminated on the porousoxygen-absorbing layer side by some method such as bonding, fusion,extrusion coating or vapor deposition, various kinds of substances willpermeate or penetrate into the micropores of the porous oxygen-absorbinglayer. This lowers porosity (particularly in the case of bonding, fusionand extrusion coating). Moreover, there are problems such as lowering ofporosity due to shrinkage of the micropores by heat (particularly in thecase of fusion and extrusion coating), insufficient strength between thelayers due to lack of contact caused by unevenness of the particles ofthe oxygen-absorbing component existing around the surface of the porousoxygen-absorbing layer (particularly in the case of bonding, fusion andextrusion coating), and insufficient resistance to gas permeation due todifficulty in continuous coating also because of the unevenness(particularly in the case of vapor deposition). Therefore, lowering ofthe oxygen absorption speed and separation of thegas-permeation-resistant layer easily tend to occur.

Accordingly, still another object of this invention is to provide alayer construction of an oxygen-absorbing film or sheet and amanufacturing method thereof in order to make the oxygen-absorbing filmor sheet by drawing the layers other than the gas-permeation-resistantlayer and then laminating the gas-permeation-resistant layer.

In order to achieve the above-described objects, this invention ischaracterized in that concerning an oxygen absorbent which comprises amultilayered body which is made of a plurality of thin resin layerslaminated over one another and which is constructed in a manner suchthat at least one layer has the oxygen-absorbing function, a non-porousoxygen-permeable layer which is permeable to oxygen is combined with aporous oxygen-permeable layer which serves as a protection layer for thenon-porous oxygen-permeable layer.

Namely, this invention is characterized in that on at least one side ofthe oxygen-absorbing layer which is prepared by dispersing theoxygen-absorbing component in a resin composition and making such aresin composition porous, one or more non-porous oxygen-permeable layersand one or more porous oxygen-permeable layers are combined andlaminated, and the respective adjacent layers are thermally bonded toeach other.

When these oxygen-permeable layers are formed on one side of theoxygen-absorbing layer, it is the oxygen absorbent of a one-sideabsorption type. When the oxygen-permeable layers are formed on bothsides, it is the oxygen absorbent of a both-side absorption type.

It is preferable that the porous oxygen-permeable layer should comprisea thin layer of a resin composition prepared by dispersing a filler(solid) in a thermoplastic resin. It is desirable that this filler behard to dissolve in water. Specifically, it is possible to use thefillers suggested in the aforementioned prior art.

In order to have a preferred oxygen permeability of the non-porousoxygen-permeable layer, it is desirable that the oxygen permeability ofthe non-porous oxygen-permeable layer be 1×10⁻¹¹ through 6×10⁻⁹ [cm³/cm².sec.Pa].

When the side of the multilayered body where the non-porousoxygen-permeable layer exists is dipped in n-heptane, if the amount ofleakage from this multilayered body is 0.3 mg or less per 1 cm² surfacearea, it is possible to almost always avoid an influence on the taste,color, properties and other factors of the content.

In the case of the oxygen-absorbing multilayered body of the one-sideabsorption type, the gas-permeation-resistant layer is laminated on theside opposite to the oxygen-absorbing side. It is preferable that thisgas-permeation-resistant layer be laminated over the oxygen-absorbinglayer through the intermediary of a buffer layer.

When the oxygen-absorbing film is constructed by including thenon-porous resin layer which should preferably be a non-polar orlow-polar macromolecules, a desirable range of oxygen permeabilityrequired for the non-porous layer is as described below.

When a pressure difference between both sides of a film having area A isp, if it takes time t for a gas having volume V to permeate through, agas permeability (P/X: P is a gas permeation coefficient and X is a filmthickness) is (P/X)=(V)/(A.p.t). However, in this case, the pressuredifference should be constant. In a definite system which is the objectof this invention, it is necessary to consider that an oxygen pressuredecreases as oxygen is absorbed and, therefore, the pressure differencedecreases. Considering this point, changes of the oxygen concentrationare not linear decreases, but are almost like exponential functionaldecreases. Accordingly, for example, if in the case of oxygen absorptionfrom an object system including air (oxygen concentration: 20.6 vol %)the 0.1 vol % oxygen concentration is determined to be anoxygen-absorbed state, the permeability of about five (log_(e)(20.6/0.1)) times as large as the value obtained by the above-mentionedexpression may be sufficient. Moreover, because of the volume of airV_(a) (V=0.206 V_(a)) and the pressure of air p_(a) (p=0.206 p_(a)), thecoefficient 0.206 is offset, thereby resulting in P/X=5V_(a)/(A.p_(a).t). If the oxygen permeability required for the non-porouslayer of the oxygen-absorbing film is calculated according to thedescription above, in the condition of p_(a) =1.013×10⁵ P_(a) (normalpressure) and with V_(a) /A=0.1-5 cm³ /cm² (most systems subject tooxygen absorption fall under this range) and t=0.5-5 days, the result isV_(a) (A.t)=0.02-10 cm³ /cm².day and P/X=1.1×10⁻¹¹ through 5.7×10⁻⁹ [cm³/cm².sec.Pa]. When oxygen is absorbed from both sides, an area valueshould be a double of the above-mentioned area of one side.

In addition to the above-described requirements on performance, thereare requirements from the manufacturing point of view as follows.Namely, considering that it is desirable to manufacture the non-porousresin layer securely on an industrial basis by using a widely useddevice in a manner such that no pinholes will be created, a thickness ofthe non-porous layer should be about 3 μm at minimum, preferably 10 μmor more, or may be about 15 μm or more when the non-porous layer is madea part of the multilayered construction.

Assuming that this non-porous layer is constructed by usingpolypropylene which is a typical non-polar macromolecules, in thecondition of oxygen permeation coefficient P=1.7×10⁻¹³[cm³.cm/cm².sec.Pa] (30° C.) (Polymer Handbook, 2nd Ed. III-235, J.Brandrup and E. H. Immergut, John Willy & Sons (1975), the units areconverted) and with thickness X>10 μm, it is applicable if P/X is withinthe range of P/X<1.7×10⁻¹⁰ [cm³ /cm².sec.Pa]. In order to usepolypropylene as a typical object in the case of Va/A=1 cm³ /cm² and t=1day, thinness of thickness X=3 μm is necessary according to the samecalculation.

Moreover, assuming that the non-porous layer is constructed by usingpolymethylpentene as a resin having a higher oxygen permeationcoefficient than that of polypropylene, in the condition of oxygenpermeation coefficient P=2.4×10⁻¹² [cm³.cm/cm².sec.Pa] (25° C.) (PolymerHandbook, 2nd Ed. III-235) and with thickness X>10 μm, it is applicableif P/X is within the range of P/X<2.4×10⁻⁹ [cm³ /cm².sec.Pa]. Even inthe case of Va/A=1 cm³ /cm² and t=1 day, thickness is X=42 μm.

As described above, as for the oxygen permeability of the non-porouslayer for the shielding purpose, it is possible to almost satisfy therequired performance if an appropriate resin is properly selected.

On the other hand, since the oxygen permeability improves if theoxygen-absorbing layer is made continuously porous, it is notparticularly necessary to limit the oxygen permeability of the resinwhich serves as a matrix component regarding the oxygen-absorbing layer.It is also possible to use a widely used resin such as polypropylene ata comparatively low price. Accordingly, if the resin used for thenon-porous layer is different from the resin used for the matrixcomponent of the oxygen-absorbing layer, it is necessary that both theselayers can be easily made multilayered.

Since this invention utilizes a granular or powder-form oxygen-absorbingcomponent, if the oxygen absorbent is constructed in a manner such thatonly the non-porous layer exists between the content and thecontinuously porous oxygen-absorbing layer, there is a possibility thatthe non-porous layer may be damaged by the oxygen-absorbing component.Therefore, it is necessary to apply some protection over the non-porouslayer and it is necessary to minimize the lowering of the oxygenpermeability caused by such a protection portion.

Next, construction examples of the oxygen-absorbing multilayered film ofthe one-side absorption type and the both-side absorption type accordingto this invention are hereinafter described by referring to thedrawings. As the oxygen-absorbing film of the one-side absorption type,FIG. 1 shows the construction of the non-porous layer (firstoxygen-permeable layer), porous layer (second oxygen-permeable layer),porous oxygen-absorbing layer, and gas-permeation-resistant layer(C/B/A/D), FIG. 2 shows the construction of the porous layer, non-porouslayer, porous oxygen-absorbing layer and gas-permeation-resistant layer(B/C/A/D), and FIG. 3 shows the construction of the non-porous layer,porous layer, porous oxygen-absorbing layer, buffer layer, adhesivelayer and gas-permeation-resistant layer (C/B/A/E/F/D). As otherconstructions, C/B/C/A/D and C/B/A/E/D are also possible.

As the oxygen-absorbing film of the both-side absorption type, FIG. 4shows the construction of the non-porous layer, porous layer, porousoxygen-absorbing layer, porous layer and non-porous layer (C/B/A/B/C).As other constructions, B/C/A/C/B and C/B/C/A/C/B/C are also possible.

As explanation of a method for manufacturing these oxygen-absorbingfilms with reference to the construction of FIG. 3, the laminated bodywhich is constructed with layer A, layer B, layer C and the buffer layer(layer E) which is made into a thin layer is drawn by the method of thisinvention and then layer D is laminated through the intermediary of theadhesive layer (layer F). Accordingly, not only a resin material, butalso various kinds of materials which are superior in resistance to gaspermeation can be used for layer D.

As the resin to construct the non-porous layer in this invention, anappropriate resin should be selected among those which are non-polar orlow-polar macromolecules and which have an appropriate oxygen permeationcoefficient P in correspondence to the required performance of theobject of oxygen absorption (or the content) as represented by theaforementioned oxygen permeability P/X. If the required performance islow, there is no special limitation. However, in order to correspond toa wider requirement range, it is desirable that P should be 1×10⁻¹³[cm³.cm/cm².sec.Pa] or more, preferably 1×10⁻¹² [cm³.cm/cm².sec.Pa] ormore if possible.

The resin to construct the non-porous layer may be not onlymacromolecules polymerized from a single monomer, but also various kindsof copolymers and resin mixtures as long as it is non-porous. Moreover,as long as the oxygen permeability of the entire non-porous layersatisfies the aforementioned range, the non-porous layer itself may beconstructed with a plurality of layers. When the same resin as that usedfor the non-porous layer is used as the resin which serves as the matrixcomponent of other layers, there is no special limitation. However, if adifferent resin is used, affinity between the resin and the resin toconstruct the non-porous layer is important. Namely, as is related to alaminating method to be described later, particularly when no adhesiveagent is used, it is desirable that the resin of the non-porous layerand the resin to be used as the matrix component of other layers shouldhave characteristics of compatibility to each other. The confirmation of"compatibility" herein referred to should not necessarily be strict interms of thermodynamics. For example, if heat sealing of both resins ispossible, the compatibility may be affirmed.

Specific examples of resins are homopolymers and copolymers of olefinegroup such as ethylene, propylene, 1-butene or 4-methyl-1-pentene,ethylene-vinyl-acetate-copolymers, polybutadiene, polyisoprene,styrene-butadiene-copolymers and hydrogenated form thereof, and variouskinds of silicon resins. Moreover, any modified form, graft form ormixture of the above-listed resins may also be used. A maximum value ofthickness of the non-porous layer is determined by the requiredperformance of the object of oxygen absorption as represented by theoxygen permeability and by the oxygen permeation coefficient of theresin. However, if it is possible to manufacture the non-porous layersecurely without creating pinholes and if it is certain that neitherpinholes nor breakage will be caused by a contact with the contentduring a normal use, it is desirable that the non-porous layer bethinner than the maximum value as much as possible. In general, it isdesirable that thickness of the non-porous layer be about 5-20 μm.

The expression "non-porous" herein means that the resin does not containany solid such as filler or oxygen-absorbing component and, for example,will not be made porous even if it is drawn.

On the other hand, the continuously porous construction which is formedin the oxygen-absorbing layer and the porous layer secures the airpermeability which is necessary for oxygen to reach the oxygen-absorbingcomponent. Specifically speaking, it is desirable that the pores areconnected to each other and a fraction of volume density of the pores tothe entire layer is 0.1 or more. From the viewpoint of strength of thelayer, it is desirable that the upper limit of such ratio be 0.9 orless, more preferably 0.5 or less.

There is no special limitation as to the position and number of thenon-porous layer in the multilayered construction as long as it islocated between the content subject to oxygen absorption and theoxygen-absorbing layer. The position and number of the non-porous layerare selected as appropriate in accordance with the use, purpose,productivity and other factors. However, considering that manufacturecan be simplified by making the total number of the layers as small aspossible, the position of the non-porous layer should be between theoxygen-absorbing layer and the continuously porous layer containing thebarely-water-soluble filler or should be on the content side of thecontinuously porous layer containing the barely-water-soluble filler,that is, an outermost layer.

If the non-porous layer is located between the oxygen-absorbing layerand the continuously porous layer containing the barely-water-solublefiller, the continuously porous layer containing thebarely-water-soluble filler acts to protect the non-porous layer againstany force from outside. If the non-porous layer is located on thecontent side of the continuously porous layer containing thebarely-water-soluble filler, the continuously porous layer containingthe barely-water-soluble filler acts to reinforce the non-porous layer.

Of the above-described constructions, the construction in which theporous layer is located on the content side does not deform so much in adirection of thickness of the non-porous layer at the time of drawingand, therefore, breakage of the non-porous layer does not occur sooften. Moreover, the above construction is superior in that after thedrawing the non-porous layer is protected against any impact given bythe content. On the other hand, the construction in which the non-porouslayer is located on the content side is superior in that even if itcontacts with a low-polar liquid, the liquid will not permeate into theinside of the multilayered body and, therefore, the oxygen absorptionperformance will not lower due to permeation of the liquid. Anappropriate layer construction should be selected by taking theabove-described advantages and disadvantages into consideration.

Various compositions are known as the oxygen-absorbing component to beused for the oxygen-absorbing layer. Among such compositions, metalpowder such as iron powder, aluminum powder and silicon powder,inorganic salts such as ferrous salt, ascorbic acid and salts thereof,alcohols or phenols such as catechol and glycerol are preferred.Particularly, those containing iron powder as a main component areappropriate. Moveover, those with iron powder and various kinds ofsalts, particularly metal halide, added therein are preferred. The mostpreferred composition is iron powder of which surface is coated withmetal halide.

As for the grain size of the oxygen-absorbing component such as ironpowder, there is no special limitation as to a grain diameterdistribution as long as a maximum grain diameter is less than thethickness of the oxygen-absorbing layer described later. However,considering the oxidation speed and no damage to (no piercing through)other layers, finer grains are preferred. However, if the grains are toofine, there is a danger of dust explosion and, therefore, carefulhandling is required. Such fine grains are also expensive in general.Therefore, a median diameter on a weight basis should be 10-100 μm, andmore preferably about 30-50 μm.

When an addition ratio of the oxygen-absorbing component to theoxygen-absorbing layer is too low, it is difficult to make the layerporous. When the addition ratio is too high, it is difficult to make thelayer into a film or sheet shape. Accordingly, the addition ratio shouldbe set by such a volume fraction that a continuously porous film will beobtained by drawing. Such a volume fraction is generally within therange of 10-60 vol %, or more preferably 20-40 vol %. If the additionratio is expressed by a weight percentage, a range of various values isavailable depending on the density of the oxygen-absorbing component.Particularly, in the case of iron powder, since it has a high density,the addition ratio by weight percentage is 40-90 wt %, or morepreferably about 60-85 wt %. If the amount of iron powder is reduced, itis possible to similarly make the layer continuously porous by addinganother filler.

Concerning the filler to be used for the continuously porous layercontaining the barely-water-soluble filler, there is no speciallimitation as long as it is an inorganic or organic substance which isinsoluble or hardly soluble in water. Assuming that the oxygen-absorbingfilm can be used also with the content which is, for example, an acidliquid, if the non-porous layer is not located on the content side, itis necessary that the oxygen-absorbing component will not leak out inthe above-described condition. Moreover, a filler such as an oxide beingin almost no danger of burning is desirable.

Because of the reasons described above, as examples of an inorganicfiller, silica, diatomaceus earth, talc, titania and barium sulfate areappropriate. As examples of an organic filler, resin particles having ahigher melting point than that of the matrix resin, and cellulose powderare appropriate. As for the grain diameter of the filler, there is nospecial limitation as long as it is within the range which allows easyhandling including the addition to the resin. From the viewpoint of notdamaging the other layers and protecting the non-porous layer as thecontinuously porous layer, it is desirable that the grain diameter beless than the thickness of the non-porous layer and even finer particlesare desirable. A 10 μm or less maximum grain diameter is preferred.

As for the resin to be used for the oxygen-absorbing layer and thecontinuously porous layer containing the barely-water-soluble filler,since both layers are made continuously porous later, the oxygenpermeability of the resin itself does not especially matter and there isno special limitation as long as the resin allows the oxygen-absorbingcomponent such as iron powder or the barely-water-soluble filler to beeasily mixed or dispersed in it. The resin should be selected byconsidering a good compatibility with the non-porous layer, easiness ofdrawing, and a working temperature range of the oxygen-absorbingmultilayered film. In general, the above-mentioned examples of resinsfor the non-porous layer apply correspondingly.

Thickness of the oxygen-absorbing layer is determined generally by atotal oxygen absorption amount. Namely, the thickness containing theoxygen-absorbing component in a minimum amount which is capable ofabsorbing the entire oxygen in the air which is subject to oxygenabsorption is the minimum thickness. Since the oxygen-absorbingcomponent in the amount twice or three times as much as the minimumamount is usually used by considering a possibility of slow inflow ofoxygen during long-term preservation of the content, the thickness isbasically twice or three times as much as the minimum thickness. Inaddition, when the oxygen-absorbing layer is made continuously porous,even the oxygen-absorbing component inside the oxygen-absorbing layerwill be directly involved in the oxygen absorption as compared with thecase where the oxygen-absorbing layer is not made porous. Accordingly,an absorption speed at the beginning increases generally in proportionto the thickness. Therefore, the thickness is determined also byconsidering the oxygen absorption speed. On the other hand, since theoxygen permeation of the non-porous layer becomes rate-determing slow,the absorption speed becomes a maximum value when the permeation speedof the non-porous layer becomes equal to the absorption speed of theoxygen-absorbing layer. A preferred thickness of the oxygen-absorbinglayer is, for example, 30 μm through 200 μm.

The continuously porous layer containing the barely-water-soluble fillerneeds to have such thickness as will allow protection or reinforcementof the non-porous layer against outside force, and prevention of damage(such as breakage caused by large iron powder) given by the particles ofthe oxygen-absorbing component to the non-porous layer. It is desirablethat the thickness of the continuously porous layer be about a half ormore of the maximum grain diameter of the oxygen-absorbing component. Onthe other hand, if it is unnecessarily too thick, the entireoxygen-absorbing film becomes too thick. Therefore, a maximum value ofthickness of this layer is about ten times as long as the maximum graindiameter of the particles of the oxygen-absorbing component.

As materials to compose the gas-permeation-resistant layer having a lowoxygen permeability, there are commonly known materials as follows: asfor resins having a low oxygen permeability, a polyester group such aspolyethylene terephthalate, a polyamide group such as nylon 6 and nylonMXD, resins containing chloride such as polyvinyl chloride andpolyvinylidene chloride, ethylene-vinyl-alcohol-copolymer, and coatedmaterials thereof; as for metals, foil or vapor deposited metal such asaluminum; and among inorganic compounds, laminated materials such asvapor deposited silicon oxide on resin. According to the properties ofthese materials, they are either previously made in a multilayered formwith other layers and then are drawn, or are bonded or fused to ordirectly evaporated on other layers which have been drawn, therebyproducing a final multilayered construction.

In the case of bonding or fusion to other layers, an adhesive layer orfusion layer may be added as necessary. If the gas-permeation-resistantlayer is directly bonded or fused to the oxygen-absorbing layer whichhas been made porous, an adhesive agent or a melted resin for fusionpenetrates into the continuous pores and the oxygen permeabilitysometimes lowers. When iron powder is used as the oxygen-absorbingcomponent, there is a fear that the bonding might become difficult dueto unevenness of the oxygen-absorbing layer as compared with a generalfilm or sheet in which a resin is solely used. As a means of avoidingthese problems, it is desirable that a buffer layer which contains as amain component the same resin as that used as the matrix component ofthe oxygen-absorbing layer or a resin having compatibility with such aresin, and which is to protect the continuous pores and to flatten thesurface should be previously laminated over the external side of theoxygen-absorbing layer, and that the layers including the buffer layerbe drawn and then the gas-permeation-resistant layer having a low oxygenpermeability be bonded or fused to the layers.

As described above, it is necessary that this buffer layer have thefunction to reduce or remove an influence of the micropores and aninfluence of the uneven surface of the porous oxygen-absorbing layer.Accordingly, it is necessary that a thickness of the buffer layer afterdrawing become no less than a minimum thickness which allows to exhibitthe above-described function. This minimum thickness generally dependson the grain diameter of the oxygen-absorbing component and adistribution thereof. As a criterion, about a half or more of the mediandiameter on a weight basis is desirable. On the other hand, there is nospecial limitation when the buffer layer is made thicker. However,considering only the point that it is necessary to satisfy theabove-described function, a maximum thickness would be about five timesas long as the maximum grain diameter of the oxygen-absorbing componentparticle. Moreover, since it is necessary that the buffer layer continueto be laminated over the porous oxygen-absorbing layer in a closelyadhered manner before and after the drawing, it is preferable that theresin to compose the buffer layer be compatible with the resin of theporous oxygen-absorbing layer. Since the buffer layer is located on thegas-permeation-resistant layer side of the oxygen-absorbing layer, theoxygen permeability of the buffer layer does not particularly matter. Asfor a thickness of the buffer layer, 20-200 μm after the drawing ispreferred. It should be noted that the descriptions about thickness oflayers hereinabove mentioned refer to thickness after the drawing.

Methods for laminating the gas-permeation-resistant layer over thebuffer layer can be mainly classified into the case where the adhesivelayer is required and the case where the adhesive layer is not required.In the case where the adhesive layer is required, there are, forexample, a bonding method by using an adhesive agent and a thermal bondor extrusion laminating method by using an adhesive resin. In the casewhere the adhesive layer is not required, there are, for example, amethod of using an adhesive resin for the buffer layer itself and avapor deposition method.

As for a gas-permeation-resistant film to be used for lamination, notonly a single layer film, but also multilayered film made by, forexample, coextrusion, extrusion laminating, extrusion coating or vapordeposition can be used. When a compatibility between the resin used forthe buffer layer and various materials used for thegas-permeation-resistant layer is low, a surface treatment may beconducted on at least one layer in order to make surface energy valuesof these layers closer to each other. It is normally desirable that thesurface treatment be conducted on the buffer layer to activate thesurface of the buffer layer.

As the surface treatment of the buffer layer, various kinds of commonlyknown chemical treatments or physical treatments can be applied. As forthe chemical treatments, there are those which utilize, for example,acid, alkali, oxidizing agents, or various kinds of reactive gases. Asfor the physical treatments, there are those which utilize, for example,flame, ultraviolet rays or plasma. Of these treatments, an appropriatetreatment is selected and applied in accordance with a combination ofthe materials of the buffer layer and the materials of thegas-permeation-resistant layer.

Because the oxygen-absorbing film or sheet of this invention includes aporous portion and a liquid might penetrate from the edges of the filmor sheet, which are not covered with the buffer layer, the physicaltreatments are superior to the other treatments in that the physicaltreatments can be conducted in a dry condition. Among these treatments,an ultraviolet ray treatment and a corona discharge treatment which isone type of a plasma treatment are especially superior because suchtreatments can be conducted simply by supplying energy (although a smallamount of oxygen in the air is used at the same time). When a thicknessof the buffer layer is small, for example, about a half of the mediandiameter of the oxygen-absorbing component, there will be almost noinfluence on the micropores of the porous oxygen-absorbing layer.However, since the influence of the uneven surface of the buffer layeris not completely extinguished, treatment conditions become severe ascompared with a normal film having a flat surface.

When the oxygen-absorbing film of this invention is used for oxygenabsorption from a system containing various kinds of liquids, it ispreferable that the oxygen-absorbing film be resistant to such liquids.When non-polar or low-polar macromolecules or their mixtures are mainlyused as resins to compose the respective layers, the oxygen-absorbingfilm is generally resistant to high-polar solvents, such as water andalcohol, and acid or alkali aqueous solutions.

However, some of these macromolecules or their mixtures are partly orcompletely dissolved by various kinds of oils or low-polar organicsolvents. For the use which requires resistance to such various kinds ofoils and low-polar organic solvents (hereinafter referred to as "oilresistance"), it is desirable that the type of resin be furtherselected. This selection is possible, for example, by measuring adissolution amount of the resin in one or more kinds of representativesolvents. If the dissolution amount is lower than a predetermined value,the resin can be used for an oil resistance use. Preferred examples ofthe resin having such oil resistance are homopolymers and/or copolymersof olefine such as ethylene, propylene, 1-butene and 4-methyl-1-pentene,and hydrogenated styrene-butadiene-copolymer.

As for the dissolution amount in the case where various kinds of filmsare used, for example, for a packaging container of food, there aregeneral standards which should be achieved. The standards in Japan areshown in the "Standards for Food and Additives" (Notification No. 370 bythe Ministry of Health and Welfare in 1959), Chapter "III. Appliancesand Container Packages," Section "D. Appliances or Container Packages orStandards for Different Materials Therefor," Item "2. Appliances orContainer Packages Made of Synthetic Resin," which are based on the"Food Sanitation Law." According to the standards, the oil resistance isdetermined by an amount of evaporation residues in n-heptane (asrepresented by a weight ratio of the evaporation residues to the weightof n-heptane after leakage) when 2 cm³ n-heptane is used per 1 cm²surface area of a film and the film is dipped in n-heptane for one hourat a temperature of 25° C. However, since the leakage is observed duringa finite time, the dissolution amount is not generally an equilibriumvalue. If this amount is no more than the standard value, the film canbe used for a packaging container. The standard value is decided foreach resin type. Examples of high standard values are 240 ppm forpolystyrene and 150 ppm for polyethylene and polypropylene. By using a0.68 g/cm³ density of n-heptane, a leakage weight per 1 cm² surface areaof the film can be found as about 0.3 mg in the case of 240 ppm asmentioned above.

As described above, if the oil resistance is required for theoxygen-absorbing film, an appropriate resin type should be selectedaccording to the above-described standards. Generally speaking, when acompatibility between the resin and the solvent is low, leakage occursfrom only around the surface of the film. When the compatibility ishigh, the solvent penetrates into the inside of the film layers and,therefore, leakage occurs also from the inside. Namely, the amount ofleakage in the case of a high compatibility is influenced by not only asurface area of the film, but also a thickness of the film. Accordingly,when the oil resistance of the oxygen-absorbing film is measured, thefilm with a fixed thickness, in other words, the film which has beenmade completely multilayered is used. Moreover, since measurement isconducted only on the side in contact with the content, theoxygen-absorbing side(s) of the oxygen-absorbing film (one side with thenon-porous layer and the porous layer disposed thereon in the case ofthe one-side absorption type, and similarly both sides in the case ofthe both-side absorption type) is/are the measurement portion(s).

The oxygen-absorbing film and sheet of this invention can be used invarious forms as the oxygen-absorbing packaging materials, for example,on a part or whole of a packaging bag or packaging container. As thecontent to be placed in the packaging bag or packaging container, notonly solids, but also liquids or both solids and liquids are possible.

As materials to compose each layer, it is possible to add various kindsof substances other than the aforementioned materials as long as a highoxygen absorption speed of the oxygen-absorbing film and the preventionof leakage of the oxygen-absorbing component and resin can be maintainedand there is no additional problem such as new leakage. As suchadditives, for example, there are pigments or dyestuff for coloring orconcealment, stabilizing components for oxidation prevention ordecomposition prevention, electrification preventing components,moisture-absorbing components, deodorizing components, plasticizingcomponents and flame retardant components. Similarly, it is possible toadd other layers such as a print layer, easily openable layer or easilypeelable layer as long as such additional layers will not have a badinfluence on the performance of the oxygen-absorbing film.

The essential point in manufacturing this invention is to laminatemultiple layers and then simultaneously draw the laminated multiplelayers together. This method makes it possible to effectively make theoxygen-absorbing layer and the layer containing the barely-water-solublefiller continuously porous and to enhance the oxygen permeability. Atthe same time, this method makes it possible to make the non-porouslayer stably thin. By the method of drawing each layer and thenlaminating them over one another (including the case where a ready-madeporous film of a single layer is used), bonding or fusion is necessaryat the time of lamination. The bonding or fusion may fill up not a fewcontinuous pores and may lower the oxygen permeability after thelamination, and also it is difficult to manufacture, bond or fuse a thinnon-porous layer.

Upon the lamination of multiple layers, it is possible to adopt normalmethods such as coextrusion, extrusion coating and extrusion laminating.The multilayered construction corresponding to this invention can beobtained by any of these methods. Of these methods, particularlypreferred methods are the extrusion coating and the extrusionlaminating, by which the layers are laminated one by one. Since a flatfilm (which has no problem in strength because it is thick especiallybefore the drawing) is once formed and then a next layer is laminated onit, for example, even when iron powder is used as the oxygen-absorbingcomponent, other layers are hardly influenced by unevenness of the ironpowder. On the other hand, the coextrusion achieves high productivity.

As generally known concerning the drawing, any of the following methodsmay be used: uniaxial drawing, biaxial simultaneous drawing or biaxialsuccessive drawing. Since it is necessary that the oxygen-absorbinglayer and the layer containing the barely-water-soluble filler be madecontinuously porous in order to achieve a high oxygen permeability andthe non-porous layer be made in a thin film form without any breakage,it is desirable that a drawing temperature be about or lower than themelting temperature of the resin of the non-porous layer and a drawingmultiplying factor be twice through twenty times on an area conversionbasis. When the above-described drawing is conducted, a thickness of themultilayered body after the drawing can be found as follows:

(Thickness before Drawing/Effective Area MultiplyingFactor)×(1/(1--Volume Fraction of Pores))

When the gas-permeation-resistant layer having a low oxygen permeabilityis added afterward, it is possible to bond or fuse such a layer by anormal method such as heat lamination, dry lamination or extrusioncoating, thereby producing a final multilayered construction. A lowoxygen permeability means that the oxygen permeation coefficient is, forexample, 1×10⁻¹⁵ (cm³.cm/cm².sec.Pa) or less.

The oxygen-absorbing film of this invention can be used as theoxygen-absorbing packaging material on a part or whole of a packagingbag or packaging container. FIG. 5 shows an example where anoxygen-absorbing film 10 of the one-side absorption type is used as atop seal film of a packaging container 40. FIG. 6 shows an example wherethe oxygen-absorbing film 10 is used for a packaging bag 50. Referencenumeral 30 corresponds to a packaged substance or content which may befixation liquid, or both solid and liquid.

FIGS. 7 and 8 show examples where an oxygen-absorbing film 20 of theboth-side absorption type is placed within a packaging bag 50 as aninside bag or partition for packaging. In the example of FIG. 8, theoxygen-absorbing film is partly molded and its edges are thermallybonded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of a construction example of theoxygen-absorbing multilayered film of a one-side absorption type (whenthe non-porous oxygen-permeable layer is made an outermost layer). FIG.2 shows a cross section of a construction example of theoxygen-absorbing multilayered film of the one-side absorption type (whenthe non-porous oxygen-permeable layer exists between the continuouslyporous layer and the continuously porous oxygen-absorbing layer). FIG. 3shows a cross section of a construction example of the oxygen-absorbingmultilayered film of the one-side absorption type (when the non-porousoxygen-permeable layer is made an outermost layer and thegas-permeation-resistant film is bonded later). FIG. 4 shows a crosssection of a construction example of the oxygen-absorbing multilayeredfilm of a both-side absorption type (when both outermost layers are thenon-porous oxygen-permeable layers). FIG. 5 shows a cross section of apackaging container for which the oxygen-absorbing multilayered film ofthe one-side absorption type is used as a top seal film. FIG. 6 shows across section of a packaging bag for which the oxygen-absorbingmultilayered film of the one-side absorption type is used on one side.FIG. 7 shows a cross section of a packaging bag for which theoxygen-absorbing multilayered film of the both-side absorption type isused as an inside bag. FIG. 8 shows a cross section of a packaging bagfor which the oxygen-absorbing multilayered film of the both-sideabsorption type is used as a partition.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is hereinafter explained in more detail byreferring to Examples and Comparative Examples. However, this inventionis not limited by such explanations. Common items in the explanationsare as follows:

As the oxygen-absorbing component, iron powder having an about 35 μmmedian diameter (maximum grain diameter: about 100 μm) was used, towhich coating was applied by spraying a calcium chloride aqueoussolution over the iron powder and then heating and drying the ironpowder. A ratio was 2 parts by weight calcium chloride to 100 parts byweight iron powder (such iron powder will be hereinafter simply referredto as "iron powder"). A mixture of 70 wt % iron powder and 30 wt % resinwas used as a material of the oxygen-absorbing layer.

As the barely-water-soluble filler, synthetic silica (CRYSTALITE VXS2made by Tatsumori Ltd.; median diameter: 5 μm) and diatomaceous earth(RADIOLITE F made by Showa Chemical Industry Co., Ltd.; median diameter:7 μm) were used. A mixture of 50 wt % synthetic silica and 50 wt %various kinds of resins or a mixture of 40 wt % diatomaceous earth and60 wt % various kinds of resins was used as materials for the layercontaining the barely-water-soluble filler, which is the layer at thestage before the porous layer. However, unless otherwise indicated, theformer mixture was used in Examples described below.

Resin components used for the respective layers and their properties areas follows:

Polypropylene (FX4D): made by Mitsubishi Chemical Corp. A product nameis polypropylene, but is actually a copolymer containing a little amountof other α-olefin. A melt flow rate is 6.0 g/10 min., a melting point is140° C., and an oxygen permeation coefficient at a temperature of 25° C.is 1.4×10⁻¹³ [cm³.cm/cm².sec.Pa].

Linear Low-Density Polyethylene (ULTZEX 2520F): made by MitsuiPetrochemical Industries, Ltd. A product name is polyethylene, but isactually a copolymer containing a little amount of other α-olefin. Amelt flow rate is 2.3 g/10 min., a melting point is 118° C., and anoxygen permeation coefficient at a temperature of 25° C. is 3.0×10⁻¹³[cm³.cm/cm².sec.Pa].

4-Methyl-1-Pentene-Copolymer (TPX MX002): made by Mitsui PetrochemicalIndustries, Ltd. A melt flow rate is 22 g/10 min. (260° C.), a meltingpoint is 235° C., and an oxygen permeation coefficient at a temperatureof 25° C. is 2.4×10⁻¹² [cm³ cm/cm².sec.Pa].

Ethylene-Propylene-Copolymer (TAFMER S-4030): made by MitsuiPetrochemical Industries, Ltd. A molar fraction of the ethylenecomponent is about 0.5. A melt flow rate is 0.2 g/10 min. (190° C.). Anoxygen permeation coefficient of this sole copolymer is unknown. Anoxygen permeation coefficient of a mixture with 50 wt % polypropylene(FX4D) at a temperature of 25° C. is 3.0×10⁻¹³ [cm³.cm/cm².sec.Pa].

Ethylene-Propylene-Copolymer (TAFMER P-0680): made by MitsuiPetrochemical Industries, Ltd. A molar fraction of the ethylenecomponent is about 0.75. A melt flow rate is 0.4 g/10 min. (190° C.). Anoxygen permeation coefficient at a temperature of 25° C. is 1.4×10⁻¹²[cm³.cm/cm².sec.Pa]. An oxygen permeation coefficient of a mixture with30 wt % linear low-density polyethylene (ULTZEX 2520F) at a temperatureof 25° C. is 8.2×10⁻¹³ [cm³.cm/cm².sec.Pa].

Mixture of Hydrogenated-Styrene-Butadiene-Copolymer and Polypropylene(DYNARON H4800N): made by Japan Synthetic Rubber Co., Ltd. A weightpercentage of polypropylene is 30 wt %. A melt flow rate is 16 g/10 min.(230° C.).

Ethylene-Vinyl-Acetate Copolymer (LV360): made by Mitsubishi ChemicalCorp. A weight percentage of vinyl acetate is 10 wt %. A melt flow rateis 9.0 g/10 min. A melting point is 95° C.

Adhesive Polyolefine (ADMER NF300): made by Mitsui PetrochemicalIndustries, Ltd. A melt flow rate is 1.3 g/10 min. (190° C.). A meltingpoint is 120° C.

Adhesive Polyolefine (ADMER NF550): made by Mitsui PetrochemicalIndustries, Ltd. A melt flow rate is 6.2 g/10 min. (190° C.). A meltingpoint is 120° C.

Nylon MXD (MX-NYLON 6007): made by MITSUBISHI GAS CHEMICAL CO., INC. Amelt flow rate is 2.0 g/10 min. A melting point is 240° C.

Ethylene-Vinyl-Alcohol-Copolymer (EVAL EP-E105): made by KURARAY CO.,LTD. A molar fraction of the ethylene component is 0.44. A melt flowrate is 5.5 g/10 min. (190° C.). A melting point is 165° C.

As the oxygen-permeation-resistant film, a nylon film (SUPERNYL made byMitsubishi Chemical Corp.) which is 15 μm thick or a lamination film ofnylon and polypropylene (which includes a thin adhesive layer betweenthe SUPERNYL nylon layer and the polypropylene layer, which is 65 μmthick in total, and which is made by Mitsubishi Chemical Corp.) wasused, and an adhesive agent for dry lamination (AD-585 and CAT-10 madeby Toyo Morton Ltd.) was used for bonding of the film.

In mixing of iron powder which is the oxygen-absorbing component and theresin or in mixing of the barely-water-soluble filler and the resin, dryblend of these materials was conducted at a predetermined weight ratioand the blended materials were then heated, melted and kneaded by usinga biaxial extrusion machine (screw diameter: 30 mm). The mixture wasextruded from a strand die, was cooled and then was cut by a pelletizer,thereby obtaining mixture pellets.

The oxygen absorption performance was measured by placing theoxygen-absorbing multilayered film having a predetermined area, apredetermined amount of air and an absorbent cotton containing water forhumidification in an oxygen-permeation-resistant bag which contains analuminum layer, and by tracing changes of an oxygen concentrationaccording to elapsed time at a temperature of 25° C. by a gaschromatograph (GC-14B made by Shimazu Corp.). As a sample formeasurement, a film cut in a size of 15 cm×20 cm was used and its edgeswere covered with a synthetic-rubber-type adhesive agent so that oxygenwould not be absorbed from the edges. The amount of air was determinedas 300 cm³ and a period of time required to reach the 0.1 vol % oxygenconcentration was measured, which was considered as an oxygen absorptiontime.

Evaluation of contamination by the iron powder which is theoxygen-absorbing component was conducted by dipping the film having apredetermined area in a 0.01N hydrochloric acid aqueous solution and bytracing changes of an amount of iron leakage in the solution accordingto elapsed time at a temperature of 25° C. by using a plasmaspectrophotometer (SPS1200VR made by Seiko Instruments Inc.).

As preparation of the evaluation, the edges of the film were firstcovered with a synthetic-rubber-type adhesive agent, and the film wasthen left in the air at a temperature of 60° C. and at 80% relativehumidity for about five days to oxidize the iron powder in the resin,thereby obtaining the film as a sample for measurement. In a case of theconstruction where the continuously porous layer containing thebarely-water-soluble filler is placed at the surface position of thefilm, not only the film was directly in an hydrochloric acid aqueoussolution, but also the water repellency of the film was previouslydiminished by ethanol and the film was then dipped in the hydrochloricacid aqueous solution. At that time, the hydrochloric acid aqueoussolution was prepared with a hydrochloric acid of atomic absorptionanalysis grade and pure water having an electric conductivity of lessthan 0.07 μS/cm and was used by placing it in a container made ofpolyethylene with a lid.

An allowable concentration of iron was set as follows: When aconcentration which may give an influence on taste by using a ferricchloride aqueous solution was examined, some changes were observed atabout 10 ppm. Therefore, an upper limit was set as 3 ppm as the valuecorresponding to iron excluding chloride. Even if the area of theoxygen-absorbing film which is a leakage source is the same, thisconcentration changes depending on a liquid amount at a place towardwhich leakage occurs. The less the liquid amount is, the higher theconcentration is. The film in a size of 15 cm×20 cm was dipped in a 1000cm³ hydrochloric acid aqueous solution, thereby the leakageconcentration was measured.

Evaluation of oil resistance was conducted in accordance with the methodindicated in the "Standards for Food and Additives" (Notification No.370 by the Ministry of Health and Welfare in 1959), Chapter "III.Appliances and Container Packages," Section "B. Testing Method forAppliances or Container Packages in General," Item "4. Testing Methodfor Evaporation Residues." That is to conduct a weight measurement ofthe amount of evaporation residues in n-heptane which has been used byhaving n-heptane in the amount of 2 cm³ per 1 cm² surface area of theoxygen-absorbing film contact the oxygen-absorbing film on theoxygen-absorbing surface side for one hour at a temperature of 25° C.Then the weight of a blank test obtained by causing n-heptane which hasnot contacted the film to evaporate is subtracted from the weightobtained by the above weight measurement, and the weight as a result ofthe subtraction is then divided by the surface area, thereby obtainingthe leakage amount per 1 cm² surface area. This value is compared withthe aforementioned standard value 0.3 mg to determine the oilresistance. For the use which does not need the oil resistance, themultilayered film can be used regardless of this evaluation.

For the actual measurement of the oil resistance, about 400 cm² (surfacearea of only one side) of the oxygen-absorbing film was cut out. Acontainer with its open portion having a 200 cm² cross-sectional areawas placed on the non-porous layer side of the oxygen-absorbing film,400 cm³ n-heptane (special grade article) was put in the container, andthe non-porous layer and n-heptane were made to contact with each otherand were left for one hour.

EXAMPLE 1

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm) and the buffer layer (300 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; the porous oxygen-absorbing layer: 60 μm;and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² (customary unit: 60 W/m²/min) discharge energy was conducted on the surface of the buffer layerof the drawn four layers, and a nylon film was then bonded to the drawnfour layers by using an adhesive agent for dry lamination (thicknessafter drying: about 10 μm), thereby producing the oxygen-absorbing filmin the following six-layer construction: the non-porous layer, theporous layer, the porous oxygen-absorbing layer, the buffer layer, theadhesive layer and the gas-permeation-resistant layer.

The oxygen absorption time was 2.0 days, the leakage of iron was 0.06ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.08 mg per 1 cm².

EXAMPLE 2

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERP-0680) and 30 wt % linear low-density polyethylene (ULTZEX 2520F) asthe non-porous layer, linear low-density polyethylene (ULTZEX 2520F) asthe resin component in the layer containing the barely-water-solublefiller and in the oxygen-absorbing layer, and linear low-densitypolyethylene (ULTZEX 2520F) as the buffer layer, four layers werelaminated by means of coextrusion in the construction and withthicknesses as follows: the non-porous layer (40 μm), the layercontaining the barely-water-soluble filler (100 μm), theoxygen-absorbing layer (100 μm) and the buffer layer (200 μm).

Uniaxial drawing of these four layers was conducted at a temperature of130° C. and at a ratio of four times in a lengthwise direction. Asummary of thickness of each layer after the drawing was: the non-porouslayer: 10 μm; the porous layer: 40 μm; the porous oxygen-absorbinglayer: 40 μm; and the buffer layer: 50 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 1.7 days, the leakage of iron was 0.09ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.02 mg per 1 cm².

EXAMPLE 3

By using 4-methyl-1-pentene-copolymer (TPX MX002) as the non-porouslayer and the buffer layer, and 4-methyl-1-pentene copolymer (TPXMX002), as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, fourlayers were laminated by means of coextrusion in the construction andwith thicknesses as follows: the non-porous layer (40 μm), the layercontaining the barely-water-soluble filler (100 μm), theoxygen-absorbing layer (200 μm) and the buffer layer (100 μm).

Uniaxial drawing of these four layers was conducted at a temperature of130° C. and at a ratio of four times in a lengthwise direction. Asummary of thickness of each layer after the drawing was: the non-porouslayer: 10 μm; the porous layer: 40 μm; the porous oxygen-absorbinglayer: 80 μm; and the buffer layer: 25 μm.

A corona discharge treatment with 1.8 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 0.7 days, the leakage of iron was 0.12ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.30 mg per 1 cm².

EXAMPLE 4

By using a mixture (DYNARON H4800N) ofhydrogenated-styrene-butadiene-copolymer and polypropylene as thenon-porous layer, polypropylene (FX4D) as the resin component in thelayer containing the barely-water-soluble filler and in theoxygen-absorbing layer, and polypropylene (FX4D) as the buffer layer,four layers were laminated by means of coextrusion in the constructionand with thicknesses as follows: the non-porous layer (100 μm), thelayer containing the barely-water-soluble filler (150 μm), theoxygen-absorbing layer (150 μm) and the buffer layer (300 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; the porous oxygen-absorbing layer: 60 μm;and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 1.3 days, the leakage of iron was 0.08ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.60 mg per 1 cm².

EXAMPLE 5

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 30 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm) and the buffer layer (300 μm).

Uniaxial drawing of these four layers was conducted at a temperature of130° C. and at a ratio of six times in a lengthwise direction. A summaryof thickness of each layer after the drawing was: the non-porous layer:17 μm; the porous layer: 70 μm; the porous oxygen-absorbing layer: 80μm; and the buffer layer: 50 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 2.1 days, the leakage of iron was 0.09ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.45 mg per 1 cm².

EXAMPLE 6

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 30 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm) and the buffer layer (300 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of four times in a lengthwisedirection and four times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 7μm; the porous layer: 30 μm; the porous oxygen-absorbing layer: 35 μm;and the buffer layer: 20 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 1.3 days, the leakage of iron was 0.08ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.24 mg per 1 cm².

EXAMPLE 7

By using ethylene-vinyl-acetate-copolymer (LV360) as the non-porouslayer, linear low-density polyethylene (ULTZEX 2520F) as the resincomponent in the layer containing the barely-water-soluble filler and inthe oxygen-absorbing layer, and linear low-density polyethylene (ULTZEX2520F) as the buffer layer, four layers were laminated by means ofcoextrusion in the construction and thicknesses as follows: thenon-porous layer (40 μm), the layer containing the barely-water-solublefiller (100 μm), the oxygen-absorbing layer (100 μm) and the bufferlayer (200 μm).

Uniaxial drawing of these four layers was conducted at a temperature of80° C. and at a ratio of four times in a lengthwise direction. A summaryof thickness of each layer after the drawing was: the non-porous layer:10 μm; the porous layer: 40 μm; the porous oxygen-absorbing layer: 40μm; and the buffer layer: 50 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 1.4 days, the leakage of iron was 0.07ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.01 mg per 1 cm².

EXAMPLE 8

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 30 wt % polypropylene (FX4D) as the non-porous layer,diatomaceus earth as the barely-water-soluble filler, polypropylene(FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm) and the buffer layer (300 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; the porous oxygen-absorbing layer: 60 μm;and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was then bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 1.2 days, the leakage of iron was 0.08ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.34 mg per 1 cm².

EXAMPLE 9

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer, andpolypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, threelayers were laminated by means of coextrusion in the construction andwith thicknesses as follows: the non-porous layer (100 μm), the layercontaining the barely-water-soluble filler (150 μm) and theoxygen-absorbing layer (150 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; and the porous oxygen-absorbing layer: 60μm.

A nylon film was bonded to the drawn three layers on the porousoxygen-absorbing layer side by using an adhesive agent for drylamination (thickness after drying: about 50 μm), thereby producing theoxygen-absorbing film in the following five-layer construction: thenon-porous layer, the porous layer, the porous oxygen-absorbing layer,the adhesive layer and the gas-permeation-resistant layer (thelamination strength of the gas-permeation-resistant layer becamesufficiently high).

The oxygen absorption time was 10 days. It seems that a part of or allthe pores in the porous oxygen-absorbing layer and the porous layer werefilled up with the adhesive agent. The leakage of iron was 0.06 ppmafter 20 days and the leakage amount from the non-porous layer side ton-heptane was 0.08 mg per 1 cm².

EXAMPLE 10

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERP-0680) and 30 wt % linear low-density polyethylene (ULTZEX 2520F) asthe non-porous layer, linear low-density polyethylene (ULTZEX 2520F) asthe resin component in the layer containing the barely-water-solublefiller and in the oxygen-absorbing layer, linear low-densitypolyethylene (ULTZEX 2520F) as the buffer layer, adhesive polyolefine(ADMER NF300) as the adhesive layer, and nylon MXD (MX-NYLON 6007) asthe gas-permeation-resistant layer, six layers were laminated by meansof coextrusion in the construction and with thicknesses as follows: thenon-porous layer (40 μm), the layer containing the barely-water-solublefiller (100 μm), the oxygen-absorbing layer (100 μm), the buffer layer(100 μm), the adhesive layer (20 μm) and the gas-permeation-resistantlayer (100 μm).

Uniaxial drawing of these six layers was conducted at a temperature of100° C. and at a ratio of four times in a lengthwise direction, therebyproducing the oxygen-absorbing film. A summary of thickness of eachlayer after the drawing was: the non-porous layer: 10 μm; the porouslayer: 40 μm; the porous oxygen-absorbing layer: 40 μm; the bufferlayer: 25 μm; the adhesive layer: 5 μm; and the gas-permeation-resistantlayer: 25 μm.

The oxygen absorption time was 1.7 days, the leakage of iron was 0.09ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.02 mg per 1 cm².

EXAMPLE 11

By using ethylene-propylene-copolymer (TAFMER P-0680) as the non-porouslayer, linear low-density polyethylene (ULTZEX 2520F) as the resincomponent in the layer containing the barely-water-soluble filler and inthe oxygen-absorbing layer, linear low-density polyethylene (ULTZEX2520F) as the buffer layer, adhesive polyolefine (ADMER NF300) as theadhesive layer, and nylon MXD (MX-NYLON 6007) as thegas-permeation-resistant layer, six layers were laminated by means ofcoextrusion in the construction and with thicknesses as follows: thenon-porous layer (40 μm), the layer containing the barely-water-solublefiller (100 μm), the oxygen-absorbing layer (100 μm), the buffer layer(100 μm), the adhesive layer (20 μm) and the gas-permeation-resistantlayer (100 μm).

Uniaxial drawing of these six layers was conducted at a temperature of100° C. and at a ratio of four times in a lengthwise direction, therebyproducing the oxygen-absorbing film. A summary of thickness of eachlayer after the drawing was: the non-porous layer: 10 μm; the porouslayer: 40 μm; the porous oxygen-absorbing layer: 40 μm; the bufferlayer: 25 μm; the adhesive layer: 5 μm; and the gas-permeation-resistantlayer: 25 μm.

The oxygen absorption time was 1.1 days, the leakage of iron was 0.13ppm after 20 days. The leakage amount from the non-porous layer side ton-heptane was 0.56 mg per 1 cm², and the almost entire non-porous layerleaked out.

EXAMPLE 12

By using a mixture of 70 wt % ethylene-propylene-copolymer (TAFMERP-0680) and 30 wt % linear low-density polyethylene (ULTZEX 2520F) asthe non-porous layer, linear low-density polyethylene (ULTZEX 2520F) asthe resin component in the layer containing the barely-water-solublefiller and in the oxygen-absorbing layer, adhesive polyolefine (ADMERNF300) as the adhesive layer, and nylon MXD (MX-NYLON 6007) as thegas-permeation-resistant layer, five layers were laminated by means ofcoextrusion in the construction and with thicknesses as follows: thenon-porous layer (40 μm), the layer containing the barely-water-solublefiller (100 μm), the oxygen-absorbing layer (100 μm), the adhesive layer(100 μm) and the gas-permeation-resistant layer (100 μm).

Uniaxial drawing of these five layers was conducted at a temperature of100° C. and at a ratio of four times in a lengthwise direction, therebyproducing the oxygen-absorbing film. A summary of thickness of eachlayer after the drawing was: the non-porous layer: 10 μm; the porouslayer: 40 μm; the porous oxygen-absorbing layer: 40 μm; the adhesivelayer: 25 μm; and the gas-permeation-resistant layer: 25 μm.

The oxygen absorption time was 1.7 days, the leakage of iron was 0.09ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.02 mg per 1 cm².

EXAMPLE 13

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm) and the buffer layer (800 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; the porous oxygen-absorbing layer: 60 μm;and the buffer layer: 90 μm.

A lamination film of nylon and polypropylene (the polypropylene side incontact with the buffer layer) was laminated by means of thermal bondover the buffer layer side of the drawn four layers, thereby producingthe oxygen-absorbing film in the following six-layer construction: thenon-porous layer, the porous layer, the porous oxygen-absorbing layer,the buffer layer, the fusion layer (polypropylene) and thegas-permeation-resistant layer (nylon). However, heating by the thermalbond was conducted only from the nylon layer side, and temperatures andheating time were set so that the porous oxygen-absorbing layer and theporous layer would not be made non-porous as much as possible.

The oxygen absorption time was 2.3 days, the leakage of iron was 0.06ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was 0.08 mg per 1 cm².

EXAMPLE 14

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer, andpolypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, threelayers were laminated by means of coextrusion in the construction andwith thicknesses as follows: the non-porous layer (100 μm), the layercontaining the barely-water-soluble filler (150 μm) and theoxygen-absorbing layer (150 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; and the porous oxygen-absorbing layer: 60μm.

A lamination film of nylon and polypropylene (the polypropylene side incontact with the porous oxygen-absorbing layer) was laminated by meansof thermal bond over the porous oxygen-absorbing layer side of the drawnthree layers, thereby producing the oxygen-absorbing film in thefollowing five-layer construction: the non-porous layer, the porouslayer, the porous oxygen-absorbing layer, the fusion layer(polypropylene) and the gas-permeation-resistant layer (nylon). However,heating by the thermal bond was conducted only from the nylon layerside, and temperatures and heating time were set so that the porousoxygen-absorbing layer and the porous layer would not be made non-porousas much as possible.

The oxygen absorption time was 15 days. It seems that a part of or allthe pores in the porous oxygen-absorbing layer and the porous layer weremade non-porous due to heat. The leakage of iron was 0.06 ppm after 20days and the leakage amount from the non-porous layer side to n-heptanewas 0.08 mg per 1 cm².

EXAMPLE 15

By using linear low-density polyethylene (ULTZEX 2520F) as thenon-porous layer and the buffer layer, and linear low-densitypolyethylene (ULTZEX 2520F) as the resin component in the layercontaining the barely-water-soluble filler and in the oxygen-absorbinglayer, four layers were laminated by means of coextrusion in theconstruction and with thicknesses as follows: the non-porous layer (40μm), the layer containing the barely-water-soluble filler (100 μm), theoxygen-absorbing layer (100 μm) and the buffer layer (800 μm).

Uniaxial drawing of these four layers was conducted at a temperature of100° C. and at a ratio of four times in a lengthwise direction. Asummary of thickness of each layer after the drawing was: the non-porouslayer: 10 μm; the porous layer: 40 μm; the porous oxygen-absorbinglayer: 40 μm; and the buffer layer: 200 μm.

A layer of adhesive polyolefine (ADMER NF550) (thickness: 15 μm) and alayer of ethylene-vinyl-alcohol-copolymer (EVAL EP-E105) (thickness: 20μm) were simultaneously laminated by means of coextrusion laminatingover the buffer layer side of the drawn four layers, thereby producingthe oxygen-absorbing film in the following six-layer construction: thenon-porous layer, the porous layer, the porous oxygen-absorbing layer,the buffer layer, the adhesive resin layer (ADMER) and thegas-permeation-resistant layer (EVAL). However, coextrusion laminatingwas conducted at such resin melting temperatures and laminating speedthat the porous oxygen-absorbing layer and the porous layer would not bemade non-porous due to heat as much as possible.

The oxygen absorption time was 2.8 days, the leakage of iron was 0.07ppm after 20 days and the leakage amount from the non-porous layer sideto n-heptane was less than 0.01 mg per 1 cm².

EXAMPLE 16

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer, andpolypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, threelayers were laminated by means of coextrusion in the construction andwith thicknesses as follows: the non-porous layer (100 μm), the layercontaining the barely-water-soluble filler (150 μm) and theoxygen-absorbing layer (150 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; and the porous oxygen-absorbing layer: 60μm.

A layer of adhesive polyolefine (ADMER NF550) (thickness: 15 μm) and alayer of ethylene-vinyl-alcohol-copolymer (EVAL EP-E105) (thickness: 20μm) were simultaneously laminated by means of coextrusion laminatingover the buffer layer side of the laminated three layers, therebyproducing the oxygen-absorbing film in the following five-layerconstruction: the non-porous layer, the porous layer, the porousoxygen-absorbing layer, the adhesive resin layer (ADMER) and thegas-permeation-resistant layer (EVAL). However, coextrusion laminatingwas conducted at such resin melting temperatures and laminating speedthat the porous oxygen-absorbing layer and the porous layer would not bemade non-porous due to heat as much as possible.

The oxygen absorption time was 12 days. It seems that a part of or allthe pores in the porous oxygen-absorbing layer and the porous layer weremade non-porous due to heat. The leakage of iron was 0.07 ppm after 20days and the leakage amount from the non-porous layer side to n-heptanewas less than 0.01 mg per 1 cm².

EXAMPLE 17

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the layer containing the barely-water-soluble filler (150 μm),the non-porous layer (100 μm), the oxygen-absorbing layer (150 μm) andthe buffer layer (300 μm).

Biaxial simultaneous drawing of these four layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the porous layer: 55 μm;the non-porous layer: 10 μm; the porous oxygen-absorbing layer: 60 μm;and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn four layers,and a nylon film was bonded to the drawn four layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following six-layerconstruction: the porous layer, the non-porous layer, the porousoxygen-absorbing layer, the buffer layer, the adhesive layer and thegas-permeation-resistant layer.

The oxygen absorption time was 2.1 days, the leakage of iron was 0.15ppm after 20 days and the leakage amount from the porous layer side ton-heptane was 0.10 mg per 1 cm².

EXAMPLE 18

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer, andpolypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, fivelayers were laminated by means of successive extrusion (the layercontaining the barely-water-soluble filler was first made into a film asa single layer, on one side of which the non-porous layer was laminatedby means of extrusion coating, and then two sets of the two-layer filmsconsisting of the layer containing the barely-water-soluble filler andthe non-porous layer were used by placing them with their front side andback side at opposite positions, and the oxygen-absorbing layer wasplaced by means of extrusion laminating between the two sets of thetwo-layer films) in the construction and with thicknesses as follows:the non-porous layer (100 μm), the layer containing thebarely-water-soluble filler (150 μm), the oxygen-absorbing layer (150μm), the layer containing the barely-water-soluble filler (150 μm) andthe non-porous layer (100 μm).

Biaxial simultaneous drawing of these five layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction, thereby producingthe oxygen-absorbing film of the both-side absorption type. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; the porous oxygen-absorbing layer: 60 μm;the porous layer: 55 μm; and the non-porous layer: 10 μm.

The oxygen absorption time was 1.0 days, the leakage of iron was 0.13ppm after 20 days and the leakage amount from one non-porous layer sideto n-heptane was 0.07 mg per 1 cm².

EXAMPLE 19

By using linear low-density polyethylene (ULTZEX 2520F) as thenon-porous layer, and linear low-density polyethylene (ULTZEX 2520F) asthe resin component in the layer containing the barely-water-solublefiller and in the oxygen-absorbing layer, five layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (40 μm), the layer containing thebarely-water-soluble filler (100 μm), the oxygen-absorbing layer (100μm), the layer containing the barely-water-soluble filler (100 μm) andthe non-porous layer (40 μm).

Uniaxial drawing of these five layers was conducted at a temperature of100° C. and at a ratio of four times in a lengthwise direction, therebyproducing the oxygen-absorbing film of the both-side absorption type. Asummary of thickness of each layer after the drawing was: the non-porouslayer: 10 μm; the porous layer: 40 μm; the porous oxygen-absorbinglayer: 40 μm; the porous layer: 40 μm; and the non-porous layer: 10 μm.

The oxygen absorption time was 1.3 days, the leakage of iron was 0.13ppm after 20 days and the leakage amount from one non-porous layer sideto n-heptane was less than 0.01 mg per 1 cm².

EXAMPLE 20

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer, andpolypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, threelayers were laminated by means of coextrusion in the construction andwith thicknesses as follows: the non-porous layer (100 μm), the layercontaining the barely-water-soluble filler (150 μm) and theoxygen-absorbing layer (150 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous layer: 55 μm; and the porous oxygen-absorbing layer: 60μm.

An attempt was made to produce the oxygen-absorbing film in thefive-layer construction of the non-porous layer, the porous layer, theporous oxygen-absorbing layer, the adhesive layer and thegas-permeation-resistant layer by bonding a nylon film to the drawnthree layers on the porous oxygen-absorbing layer side by using anadhesive agent for dry lamination (thickness after drying: about 10 μm).When the side to which the adhesive agent was applied was made theporous oxygen-absorbing layer side, the adhesive agent was considerablyabsorbed by the porous oxygen-absorbing layer. When the side to whichthe adhesive agent was applied was made the nylon film side, the contactarea of the adhesive agent layer with the porous oxygen-absorbing layerbecame insufficient. In both cases, the gas-permeation-resistant layercame out to be easily peelable. Therefore, it was found that it ispreferable to provide the aforementioned buffer layer in order toenhance adhesiveness between the oxygen-absorbing layer and thegas-permeation-resistant layer.

Comparative Example 1

By using polypropylene (FX4D) as the resin component in the layercontaining the barely-water-soluble filler and in the oxygen-absorbinglayer, and polypropylene (FX4D) as the buffer layer, three layers werelaminated by means of coextrusion in the construction and withthicknesses as follows: the layer containing the barely-water-solublefiller (150 μm), the oxygen-absorbing layer (150 μm) and the bufferlayer (300 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the porous layer: 55 μm;the porous oxygen-absorbing layer: 60 μm; and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn three layers,and a nylon film was then bonded to the drawn three layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following five-layerconstruction: the porous layer, the porous oxygen-absorbing layer, thebuffer layer, the adhesive layer and the gas-permeation-resistant layer.

The oxygen absorption time was 0.6 days, the leakage of iron was 2 ppmafter 20 days (26 ppm after 20 days when the oxygen-absorbing film waspreviously dipped in ethanol for about one minute before dipping in thehydrochloric acid aqueous solution) and the leakage amount from thegas-permeation-resistant layer side to n-heptane was less than 0.01 mgper 1 cm².

Comparative Example 2

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the oxygen-absorbinglayer, and polypropylene (FX4D) as the buffer layer, three layers werelaminated by means of coextrusion in the construction and withthicknesses as follows: the non-porous layer (100 μm), theoxygen-absorbing layer (150 μm) and the buffer layer (300 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the non-porous layer: 10μm; the porous oxygen-absorbing layer: 60 μm; and the buffer layer: 35μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn three layers,and a nylon film was then bonded to the drawn three layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the oxygen-absorbing film in the following five-layerconstruction: the non-porous layer, the porous oxygen-absorbing layer,the buffer layer, the adhesive layer and the gas-permeation-resistantlayer.

The oxygen absorption time was 1.9 days, the leakage of iron was 1.1 ppmafter 20 days, and the leakage amount from the non-porous layer side ton-heptane was 0.09 mg per 1 cm². As a result of observation with anoptical microscope, a little amount of iron powder which penetratedthrough the non-porous layer was confirmed.

Comparative Example 3

By using a mixture of 50 wt % ethylene-propylene-copolymer (TAFMERS-4030) and 50 wt % polypropylene (FX4D) as the non-porous layer,polypropylene (FX4D) as the resin component in the layer containing thebarely-water-soluble filler and in the oxygen-absorbing layer, andpolypropylene (FX4D) as the buffer layer, four layers were laminated bymeans of coextrusion in the construction and with thicknesses asfollows: the non-porous layer (25 μm), the layer containing thebarely-water-soluble filler (20 μm), the oxygen-absorbing layer (150 μm)and the buffer layer (200 μm).

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the four layers whichwere not drawn, and a nylon film was then bonded to the four layers byusing an adhesive agent for dry lamination (thickness after drying:about 10 μm), thereby producing the oxygen-absorbing film in thefollowing six-layer construction: the non-porous layer, the layercontaining the barely-water-soluble filler, the oxygen-absorbing layer,the buffer layer, the adhesive layer and the gas-permeation-resistantlayer.

The oxygen absorption time was 40 days, the leakage of iron was 0.03 ppmafter 20 days, and the leakage amount from the non-porous layer side ton-heptane was 0.12 mg per 1 cm².

Comparative Example 4

By using polypropylene (FX4D) as the resin component in the layercontaining the barely-water-soluble filler and in the oxygen-absorbinglayer, and polypropylene (FX4D) as the buffer layer, three layers werelaminated by means of coextrusion in the construction and withthicknesses as follows: the layer containing the barely-water-solublefiller (150 μm), the oxygen-absorbing layer (150 μm) and the bufferlayer (300 μm).

Biaxial simultaneous drawing of these three layers was conducted at atemperature of 130° C. and at a ratio of three times in a lengthwisedirection and three times in a widthwise direction. A summary ofthickness of each layer after the drawing was: the porous layer: 55 μm;the porous oxygen-absorbing layer: 60 μm; and the buffer layer: 35 μm.

A corona discharge treatment with 3.6 kJ/m² discharge energy wasconducted on the surface of the buffer layer of the drawn three layers,and a nylon film was then bonded to the drawn three layers by using anadhesive agent for dry lamination (thickness after drying: about 10 μm),thereby producing the following five-layer construction: the porouslayer, the porous oxygen-absorbing layer, the buffer layer, the adhesivelayer and the gas-permeation-resistant layer.

Moreover, an attempt was made to add the non-porous layer (thickness: 10μm) on the porous layer side of the five-layer construction by means ofextrusion coating by using a mixture of 50 wt %ethylene-propylene-copolymer (TAFMER S-4030) and 50 wt % polypropylene(FX4D). Probably due to insufficient quantity of heat of the meltedresin and also due to slight unevenness of the porous layer portion,fusion could not be performed with the 10 μm thickness and thelamination was impossible.

Industrial Applicability

The oxygen-absorbing film and sheet of the present invention is a newoxygen absorbent which has both a high oxygen absorption speed and thecapability to prevent contamination by the oxygen-absorbing component.The oxygen-absorbing film and sheet of this invention is applicable notonly to a system which contains a small amount of liquid components andwhich has been a main object of conventional oxygen absorbers, but alsoto a system containing a large amount of various kinds of liquidcomponents. The oxygen-absorbing film and sheet of this invention can beused to compose containers and packages which are aimed at preventingvarious kinds of products such as food, medicines and metal products,which easily deteriorate due to an influence of oxygen, from oxidizing.Moreover, this invention makes it possible to freely laminate thegas-permeation-resistant layer afterward with regard to such anoxygen-absorbing film and sheet and to enhance the applicability inmanufacture of the gas-permeation-resistant layer portion and the useafter lamination.

What is claimed is:
 1. An oxygen-absorbing multilayered body, comprisinga multilayered body with a plurality of resin layers laminated over oneanother to form at least one laminated side, said laminated side of thismultilayered body being constructed as an oxygen-absorbing surface and,if there is a surface which is not an oxygen-absorbing surface saidmultilayered body being constructed as having a gas-permeation-resistantlayer on said surface,said multilayered body including: a porousoxygen-absorbing layer including an oxygen-absorbing component in athermoplastic resin; a non-porous oxygen-permeable layer which ispermeable to oxygen; and a porous oxygen-permeable layer which serves asa protection layer for the non-porous oxygen-permeable layer, wherein onat least one side of said porous oxygen-absorbing layer one or more ofsaid non-porous oxygen-permeable layer and one or more of said porousoxygen-permeable layer are combined and laminated over one another toform a laminate, and said resulting laminate is drawn to enlarge poresin said porous layers.
 2. An oxygen-absorbing multilayered bodyaccording to claim 1, wherein said porous oxygen-permeable layercomprises a layer of a resin composition made by dispersing a filler ina thermoplastic resin.
 3. An oxygen-absorbing multilayered bodyaccording to claim 1, wherein said oxygen-absorbing component containsiron powder as its main element.
 4. An oxygen-absorbing multilayeredbody according to claim 1, wherein the oxygen permeability of saidnon-porous oxygen-permeable layer is 1×10⁻¹¹ through 6×10⁻⁹ cm³/cm².sec.Pa.
 5. An oxygen-absorbing multilayered body according to claim1, wherein when the oxygen-absorbing surface side of said multilayeredbody is dipped in n-heptane, the leakage amount from the multilayeredbody is 0.3 mg or less per 1 cm² surface area.
 6. An oxygen-absorbingmultilayered body according to claim 1, wherein said multilayered bodyis formed in a sheet or film shape.
 7. An oxygen-absorbing multilayeredbody according to claim 1, wherein only one side of said multilayeredbody is constructed as the oxygen-absorbing surface, and on one side ofsaid oxygen-absorbing layer one or more said non-porous oxygen-permeablelayers and one or more porous oxygen-permeable layers are combined andlaminated over one another, and the gas-permeation-resistant layer islaminated over the non-oxygen-absorbing surface of said oxygen-absorbinglayer, thereby said multilayered body is designed to absorb oxygen fromone side of said oxygen-absorbing layer.
 8. An oxygen-absorbingmultilayered body according to claim 7, wherein saidgas-permeation-resistant layer is laminated over said oxygen-absorbinglayer through the intermediary of a buffer layer which enhances adhesionof the gas-permeation-resistant layer when it is laminated over theoxygen-absorbing layer.
 9. An oxygen-absorbing multilayered bodyaccording to claim 1, wherein both sides of said multilayered body areconstructed as the oxygen-absorbing surfaces, and on both sides of saidoxygen-absorbing layer one or more said non-porous oxygen-permeablelayers and one or more said porous oxygen-permeable layers are combinedand laminated over one another.
 10. An oxygen-absorbing multilayeredbody according to claim 1, wherein on at least one side of saidoxygen-absorbing layer the porous oxygen-permeable layer and thenon-porous oxygen-permeable layer are laminated in the order listedabove as counted from the oxygen-absorbing layer.
 11. Anoxygen-absorbing multilayered body according to claim 1, wherein on atleast one side of said oxygen-absorbing layer the non-porousoxygen-permeable layer and the porous oxygen-permeable layer arelaminated in the order listed above as counted from the oxygen-absorbinglayer.
 12. An oxygen-absorbing multilayered body according to claim 1,wherein pores formed in said oxygen-absorbing layer and said porouslayer are interlinked to each other.
 13. An oxygen-absorbingmultilayered body according to claim 1, wherein the volume density ofthe pores formed in said oxygen-absorbing layer and said porous layer inthe entire layers ranges from 0.1 to 0.9.
 14. The oxygen-absorbingmultilayered body according to claim 1, wherein the volume density ofthe pores formed in said oxygen-absorbing layer and said porous layer inthe entire layers ranges from 0.1 to 0.5.
 15. An oxygen-absorbingmultilayered body according to claim 1, wherein the thickness of saidoxygen-absorbing layer is from 30 μm to 200 μm.
 16. A method formanufacturing an oxygen absorbent which comprises a multilayered bodywith a plurality of thin resin layers laminated over one another, atleast one laminated side of this multilayered body being constructed asan oxygen-absorbing surface and, if there is a surface which is not anoxygen-absorbing surface, said multilayered body being constructed ashaving a gas-permeation-resistant layer on said surface, comprising thesteps of:laminating said non-porous oxygen-permeable layer, said porousoxygen-permeable layer and said porous oxygen-absorbing layer to form alaminate, and drawing said laminate to enlarge pores in said porouslayers.
 17. A method according to claim 16, wherein uniaxial or biaxialdrawing of said multilayered body is connected at least in an uniaxialdirection to a ratio of twice through twenty times on an area conversionbasis.
 18. A method for manufacturing an oxygen absorbent according toclaim 16, wherein said porous oxygen-permeable layer comprises a thinlayer of a resin composition which is made by dispersing a granularwater-soluble filler in a thermoplastic resin.
 19. A method formanufacturing an oxygen absorbent according to claim 16, wherein saidmultilayered body is made by combining and laminating one or more saidnon-porous oxygen-permeable layers and one or more said porousoxygen-permeable layers on one side of said oxygen-absorbing layer andby laminating the gas-permeation-resistant layer on the other side ofsaid oxygen-absorbing layer.
 20. A method according to claim 19, whereinsaid multilayered body is formed by laminating a buffer layer betweensaid oxygen-absorbing layer and said gas-permeation-resistant layer. 21.A method according to claim 16, wherein said multilayered body is formedby combining one or more said non-porous oxygen-permeable layers and oneor more said porous oxygen-permeable layers on both sides of saidoxygen-absorbing layer.
 22. An oxygen-absorbing multilayered bodycomprising:a porous oxygen-absorbing layer comprising anoxygen-absorbing component and a thermoplastic resin; non-porousoxygen-permeable layers which are permeable to oxygen; and porousoxygen-permeable layers which serve as protection layers for thenon-porous oxygen-permeable layers, wherein said non-porousoxygen-permeable layers and said porous oxygen-permeable layers areprovided in this order on both sides of said oxygen-absorbing layer, andwherein the non-porous layers, the porous layers, and the porousoxygen-absorbing layers are laminated and are then drawn to enlargepores in said porous layers, thereby forming the oxygen-absorbingmultilayered body.
 23. An oxygen-absorbing multilayered bodycomprising:a porous oxygen-absorbing layer comprising anoxygen-absorbing component and a thermoplastic resin; porousoxygen-permeable layers which serve as protection layers for thenon-porous oxygen-permeable layers; non-porous oxygen-permeable layerswhich are permeable to oxygen; wherein said porous oxygen-permeablelayers and said non-porous oxygen-permeable layers are provided in thisorder on both sides of said oxygen-absorbing layer, and wherein theporous layers, the non-porous layers, and the porous oxygen-absorbinglayer are laminated and are then drawn to enlarge pores in said porouslayers, thereby forming the oxygen-absorbing multilayered body.
 24. Amethod for manufacturing an oxygen-absorbing multilayered body whichincludes a porous oxygen-absorbing layer comprising an oxygen-absorbingcomponent and a thermoplastic resin; a non-porous oxygen-permeable layerwhich is permeable to oxygen; and a porous oxygen-permeable layer whichserves as a protection layer for the non-porous oxygen-permeable layer,comprising the steps of:providing said non-porous oxygen-permeable layerand said porous oxygen-permeable layer on both sides of saidoxygen-absorbing layer, and laminating the non-porous layer, the porouslayer, and the porous oxygen-absorbing layer to form a laminate, anddrawing the resulting laminate to enlarge pores in said porous layers.25. An oxygen-absorbing multilayered body comprising, in the orderlisted below:a gas-permeation-resistant layer; a porous oxygen-absorbinglayer comprising an oxygen-absorbing component and a thermoplasticresin; a porous oxygen-permeable layer comprising a filler and athermoplastic resin; and a non-porous oxygen-permeable layer made of atleast one thermoplastic resin selected from a group consisting ofhomopolymers and copolymers of polyethylene, polypropylene,poly-1-butene, poly-4-methyl-1-pentene,ethylene-vinyl-acetate-copolymer, polybutadiene, polyisoprene,styrene-butadiene-copolymer and hydrogenated form thereof, and anymodified form and graft form of the above-listed resins, said non-porousoxygen-permeable layer being heat-sealable, wherein on at least one sideof said porous oxygen-absorbing layer one or more of said non-porousoxygen-permeable layer and one or more of said porous oxygen-permeablelayer are combined and laminated over one another to form a laminate,and the resulting laminate is drawn to enlarge pores in said porouslayers.
 26. A method for manufacturing an oxygen-absorbing multilayeredbody which comprises, in the order listed below:agas-permeation-resistant layer made of gas-permeation-resistant resin; aporous oxygen-absorbing layer comprising an oxygen-absorbing componentand a thermoplastic resin; a porous oxygen-permeable layer comprising afiller and a thermoplastic resin; and a non-porous oxygen-permeablelayer being heat-sealable, wherein the non-porous layer, the porouslayer, the porous oxygen-absorbing layer and the gas-permeationresistant layer are formed by being laminated and then drawn to enlargepores in said porous layers.
 27. A method for manufacturing anoxygen-absorbing multilayered body which comprises, in the order listedbelow:a gas-permeation-resistant layer; a porous oxygen-absorbing layercomprising an oxygen-absorbing component and a thermoplastic resin; anda porous oxygen-permeable layer comprising a filler and a thermoplasticresin, wherein a non-porous layer, the porous layer and the porousoxygen-absorbing layer are formed by being laminated and then drawn toform a layered body to enlarge pores in said porous layers, andsubsequently the gas-permeation-resistant layer is laminated thereon.